diff --git a/include/boost/system/error_code.hpp b/include/boost/system/error_code.hpp
index 57e7175..ad9f454 100644
--- a/include/boost/system/error_code.hpp
+++ b/include/boost/system/error_code.hpp
@@ -732,10 +732,14 @@ inline const error_category & generic_category() BOOST_SYSTEM_NOEXCEPT
     inline system::error_code* throws()
     {
       // See github.com/boostorg/system/pull/12 by visigoth for why the return
-      // is poisoned with (1) rather than (0). A test, test_throws_usage(), has
-      // been added to error_code_test.cpp, and as visigoth mentioned it fails
-      // on clang for release builds with a return of 0 but works fine with (1).
-      return reinterpret_cast<system::error_code*>(1);
+      // is poisoned with nonzero rather than (0). A test, test_throws_usage(),
+      // has been added to error_code_test.cpp, and as visigoth mentioned it
+      // fails on clang for release builds with a return of 0 but works fine
+      // with (1).
+      // Since the undefined behavior sanitizer (-fsanitize=undefined) does not
+      // allow a reference to be formed to the unaligned address of (1), we use
+      // (8) instead.
+      return reinterpret_cast<system::error_code*>(8);
     }
   }
 
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 55e41c0..784fd8e 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -125,6 +125,7 @@ else
          [ run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>static : single_instance_lib_static ]
          [ run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>shared : single_instance_lib_shared ]
          [ system-run before_main_test.cpp ]
+         [ run-fail throws_assign_fail.cpp ]
          [ system-run- constexpr_test.cpp ]
          ;
 
diff --git a/test/error_code_test.cpp b/test/error_code_test.cpp
index 1f96c59..7965541 100644
--- a/test/error_code_test.cpp
+++ b/test/error_code_test.cpp
@@ -22,7 +22,6 @@
 #include <cstring>
 #include <functional>
 #include <boost/cerrno.hpp>
-#include <boost/config/pragma_message.hpp>
 
 //  Although using directives are not the best programming practice, testing
 //  with a boost::system using directive increases use scenario coverage.
@@ -247,17 +246,8 @@ int main( int, char ** )
   BOOST_TEST( econd.message() != "" );
   BOOST_TEST( econd.message().substr( 0, 13) != "Unknown error" );
 
-#if !defined(UBSAN)
-
-  // the current implementation of boost::throws() relies on undefined behavior
   test_throws_usage();
 
-#else
-
-  BOOST_PRAGMA_MESSAGE("Skipping test_throws_usage() due to UBSAN");
-
-#endif
-
 #ifdef BOOST_WINDOWS_API
   std::cout << "Windows tests...\n";
   // these tests probe the Windows errc decoder
diff --git a/test/throws_assign_fail.cpp b/test/throws_assign_fail.cpp
new file mode 100644
index 0000000..8453577
--- /dev/null
+++ b/test/throws_assign_fail.cpp
@@ -0,0 +1,28 @@
+
+// Copyright 2018 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+
+#include <boost/system/error_code.hpp>
+
+using namespace boost::system;
+
+static void f( error_code & ec )
+{
+    ec = error_code();
+}
+
+#if defined(_WIN32)
+# include <windows.h> // SetErrorMode
+#endif
+
+int main()
+{
+#if defined(_WIN32)
+
+    SetErrorMode( SetErrorMode( 0 ) | SEM_NOGPFAULTERRORBOX );
+
+#endif
+
+    // this should crash
+    f( boost::throws() );
+}